How to update Facebook app in iPhone 11?

Open the App Store app, tap on your user icon at the top right, scroll down to the Update section and see if there's an update available for Facebook. If there is, tap on the Update button.

If you are having a specific issue, then explain what that is.

No, if you are running iOS 17, updates is no longer at the bottom of the main screen.

You need to tap on your User icon at the top right, and then scroll down to the Updates section.

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Facebook is not an Apple product. Contact facebook for support of their products and services.